Molecular design and syntheses of new polycyclic dithiines and quinoid dyes for 3rd order nonlinear optical materials were studied. These dyes have large pi-conjugated systems and intramolecular charge-transfer chromophoric systems. A wide and planar structure of dye molecule with strong intra-and intermolecular hydrogen bonding are very important to produce strong intermolecular pi-pi interactions of dye molecules in crystals or thin film for NLO devices. This system has large photoinduced polarization which is favorable for 3rd order NLO materials.On the other hand, intermolecular CT complexes composed of polycyclic dithiines with TCNQ were also synthesized and their NLO responses were evaluated.Some quinoid dyes produce three dimensional molecular stacking in crystals by interlayr pi-pi interactions which play a great role to produce a large CHI^<(3)> value. We found two types of new quinoid dyes, 4,8-dihydroxy-2,6-bis (butylamino) -1,5-naphthoquinone and 1,4-dithioketo-3,6-diphenylpyrrolo [3,4-c] pyrrole, which were one of the candidates for 3rd order NLO materials.